Apparatus for reducing microbe content in foodstuffs by pH and physical manipulation

ABSTRACT

A manipulating apparatus (10) receives a plurality of previously frozen pieces of pH modified foodstuffs or workpieces (23) and physically manipulates or stresses the workpieces while they remain in a frozen state. The physical manipulation causes relative movement between various points within the volume of the workpieces (23) and kills microbes within the foodstuff . One preferred pH modifying arrangement includes a supply of NH3 gas (11) and a pump (9) for placing the comminuted foodstuffs to be processed and the NH3 gas together under an operating pressure for a period of time sufficient to increase the pH of the foodstuffs.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of pending U.S. patentapplication Ser. No. 09/144,928, filed Sep. 1, 1998, now U.S. Pat. No.6,054,164.

TECHNICAL FIELD OF THE INVENTION

This invention relates to food processing, and more particularly, toreducing microbe content in processed foodstuffs. The inventionencompasses both an apparatus and method for manipulating the pH offoodstuffs and then physically manipulating the foodstuffs to reducemicrobe content.

BACKGROUND OF THE INVENTION

Most foods are processed in some way before reaching the consumer. Forexample, vegetables may be washed, trimmed, blanched, and than frozenprior to distribution. Meat products also require significant processingbefore reaching the consumer. At the very least, the animal carcass iscut into segments and the larger cuts of meat or fillets are cut fromthese initial segments. Other usable elements remaining after separatingthe larger cuts of meat are then separated from the remaining unusableelements such as bone and then ground or chopped, mixed, and thencommonly frozen for distribution.

Foodstuffs are inevitably exposed to microbes as the foodstuffs areprocessed or handled. Microbes are part of the natural decay process oforganic material and may be deposited on foodstuffs through the air orby contact between the foodstuff and contaminated equipment or othermaterial. Although some microbes may be relatively benign, otherscontribute to spoilage and some can cause serious illness. Lactic acidproducing bacteria are examples of benign microbes, while some strainsof E. Coli, Salmonella, Listeria, and Staph bacteria are examples ofpathogenic microbes which can cause serious illness when ingested byhumans.

Even with careful processing practices, foodstuffs may be exposed topathogenic microbes during processing or initial handling. The risk ofillness from dangerous microbes which may be present in foodstuffs isreduced by a careful handling and cooking by the consumer. In largercuts of meat for example, dangerous microbes may only be present on thesurface of the meat and are readily killed in the cooking process.

Ground or chopped and mixed foodstuffs, including ground beef, may carrydangerous microbes which are killed only after thoroughly cooking thematerial. The reason for this is that dangerous microbes residing at thesurface of a larger piece of the foodstuff may be distributed throughoutthe final ground or chopped product as the large piece is ground andmixed together with other pieces. Thorough cooking is required in orderto kill microbes residing in the center of a piece of ground and mixedfoodstuff.

It is desirable to control the growth of microbes and reduce microbecontent in foodstuffs. Microbe content and growth in foodstuffs may bereduced by applying chemical additives or preservatives to thefoodstuff. These chemical additives or preservatives, however, may notbe acceptable to consumers, or may have undesirable effects onfoodstuffs.

Alternatively to chemical additives or preservatives, heat may be usedto kill microbes in foodstuffs. However, heat processing orsterilization often has undesirable effects on the quality orcharacteristics of the foodstuff and may make the food productundesirable to the consumer.

SUMMARY OF THE INVENTION

It is a broad object of the invention to provide a method for reducingmicrobe content in foodstuffs, particularly meats, and to provide anapparatus for performing the method.

The method of the invention comprises modifying the pH of a foodstuffand then physically manipulating or applying stress to the foodstuffwhile the foodstuff is in a frozen state. The physical manipulationproduces significant relative movement within the foodstuff. In thissense “relative movement” means movement between one point in thefoodstuff and adjacent points in the foodstuff. While the mechanism bywhich the process reduces live microbe count is not fully understood, pHmodification followed by physical manipulation according to inventionhas been shown to significantly reduce microbe content in the treatedfoodstuffs.

The process according to the invention may be performed as a continuousprocess or as a batch process. In either case, the pH of the foodstuffto be processed is first modified by suitable means. After the pHmodification, the foodstuff is cooled by a suitable freezer to a processtemperature no greater than or below the freezing point of the foodstuffto place the foodstuff in a frozen state. As used in this disclosure andthe accompanying claims, the “freezing point of the foodstuff” means thetemperature at which ice crystals begin to form in the foodstuff to beprocessed. The frozen foodstuff is then formed into workpieces. Amanipulating arrangement then manipulates the frozen workpieces toproduce relative movement preferably throughout each workpiece. Themanipulating arrangement may define a working area and operate tomanipulate each workpiece as it passes or is drawn through the workingarea.

The pH of the foodstuff may be modified in any suitable manner. Forexample, a higher pH foodstuff such as lean finely textured beef may bemixed with a regular ground beef to modify the pH of the resultingmixture. The process of producing lean finely textured beef, whichincreases pH with respect to the starting material, also represents asuitable pH modifyng step. Also, a foodstuff may be placed in contactwith NH₃ (Ammonia) in gaseous or aqueous form to increase the pH of thefoodstuff. U.S. patent application Ser. No. 08/803,322, now U.S. Pat.No. 5,871,795, the disclosure of which is hereby incorporated herein bythis reference, discloses a pH modifying apparatus and method which maybe employed in this invention. pH modification within the scope of theinvention also encompasses decreasing pH. pH of a foodstuff may bedecreased by placing the foodstuff in contact with a pH reducingmaterial such as CO₂, for example.

In one form of the invention, the manipulating arrangement comprisesfirst and second spaced apart rollers, with the working area definedbetween the first and second rollers. The rollers are preferably drivenin a counter-rotating fashion to draw a workpiece there between. Thespacing between the first and second rollers is smaller than an initialthickness of each workpiece so that each frozen workpiece is compressedand allowed to spread out laterally as it passes between the rollers.

Each roller may include a plurality of the spaced apart longitudinalridges. The ridged rollers may be rotated such that each ridge on oneroller registers with the space between a pair of adjacent ridges on theopposite roller as the rollers are rotated, similar to the cogs of twointermeshed gears. However, the ridges preferably do not touch, butmaintain a minimum clearance. This ridged roller form of manipulatingarrangement has the advantage that the frozen workpiece not only spreadsout laterally as it is drawn between the rollers but is also bentbetween the opposing ridges on the counter-rotating rollers.

Another form of manipulating arrangement within the scope of theinvention comprises two opposing plates with a suitable actuator, oractuators, for pressing the opposing plates together. The processincludes placing a plurality of workpieces between the two plates andthen operating the actuator arrangement to press the plates together tosignificantly reduce the volume between the plates. The relativemovement of the plates presses the previously frozen workpieces into ablock of frozen material, In this arrangement, the desired relativemovement in the workpieces occurs as the workpieces deform to fill thevoids left between adjacent workpieces when the workpieces wereinitially placed in the area between the opposing plates.

Regardless of the particular manipulating arrangement employed tomanipulate the frozen workpieces according to the invention, amanipulator temperature control system preferably controls thetemperature of the manipulating arrangement surfaces which come incontact with the frozen workpieces. The manipulator temperature controlsystem may cool the surfaces of the manipulating arrangement to ensurethat heat from the surfaces of the manipulating arrangement does notraise the temperature of the workpieces to a temperature above thedesired process temperature. Alternatively, the manipulator temperaturecontrol system may heat the manipulating arrangement surfaces andthereby heat the frozen workpieces from a lower process temperature tothe freezing temperature or even slightly above the freezingtemperature. Also, maintaining the surfaces of the manipulatingarrangement at a temperature near the process temperature or slightlyabove the process temperature also helps prevent the workpieces fromsticking to the manipulator surfaces.

These and other objects, advantages, and features of the invention willbe apparent from the following description of the preferred embodiments,considered along with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of a foodstuff pH and physicalmanipulation system embodying the principles of the invention.

FIG. 2 is a partial longitudinal section view of a manipulatingarrangement shown diagrammatically in FIG. 1.

FIG. 3 is a partial transverse section view taken along line 3—3 in FIG.2.

FIG. 4 is an enlarged diagrammatic side view of a piece of foodstuffbeing drawn between the rollers of a preferred manipulating arrangement.

FIG. 5 is a view in section taken along line 5—5 in FIG. 4.

FIG. 6 is a view in section taken along line 6—6 in FIG. 4.

FIG. 7 is a partial section view showing an alternate manipulatingarrangement embodying the principles of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 an apparatus. 10 for manipulating foodstuffs isassociated with a pH manipulating system 8 and a suitable freezer 12. Atransport device 14 is positioned between the freezer 12 andmanipulating apparatus 10. A second to transport device 16 may bepositioned at an outlet from the manipulating apparatus 10 fortransporting treated foodstuffs to further processing equipment.

The illustrated pH manipulating system 8 includes a pump 9, NH₃ supply11, pressure reduction arrangement 13, and a system 15 for removingexcess NH₃. Conduit 17 transfers pH modified foodstuff to freezer 12.Pump 9 preferably comprises a piston pump with an injection arrangement(not shown) for injecting a measured amount of NH₃ from supply 11 intothe foodstuff stream either during compression or prior to compression.The pump preferably compresses the NH₃ and foodstuff to a pressure at orabove the vapor pressure of the NH₃ at the temperature of the foodstuff.As disclosed in U.S. patent application Ser. No. 08/803,322, now U.S.Pat. No. 5,871,795, this treatment pressure has been found to rapidlyincrease the pH of foodstuffs. Pressure reduction arrangement 13 maycomprise any suitable device or arrangement for releasing the pressuredeveloped by pump 9. Device 15 may comprise an arrangement for applyinga vacuum or any other arrangement for drawing off excess NH₃ after thetreatment pressure is released at device 13.

Those skilled in the art will appreciate that many arrangements otherthan the system 8 shown in FIG. 1 may be used to modify the pH of thefoodstuff. For example, the foodstuff may be treated in batches in avessel into which a suitable pH modifying gas is introduced.

Also, a liquid material such as aqueous NH₃ may be applied to thefoodstuff under pressure or otherwise. Any pH modifying material may beused to modify the pH of the foodstuff within the scope of theinvention. Although the invention preferably comprises increasing the pHof the foodstuff, pH modification within the scope of the invention alsoencompasses decreasing the pH of the foodstuff. Decreasing the pH may beaccomplished by applying a pH decreasing material such as CO₂ gas to thefoodstuff preferably under pressure as described above with reference toFIG. 1. Furthermore, no pH modifying material may be needed forprocessing certain foodstuffs. For example, reducing the fat content ofa comminuted beef product may change the pH of the material sufficientlywithin the scope of the invention, as may mixing a reduced fat productwith a regular comminuted product.

The pH modification required according to the invention may be minimal.However, the pH modification step according to the invention preferablycomprises modifying the pH of the foodstuff by at least approximately 3%from the original pH of the foodstuff. For example, a foodstuff havingan original pH of approximately 5.5 is preferably treated to increaseits pH to at least approximately 5.67. Treatment times to modify the pHmay range from on the order of approximately one second to three minutesor more.

Freezer 12 freezes the pH modified foodstuff and cutter 18 cuts thefrozen foodstuff into workpieces which are then placed on transportdevice 14. Transport device 14 transports the workpieces to manipulatingapparatus 10. Manipulating apparatus 10 physically manipulates thefrozen foodstuff to produce relative movement between different pointsin the volume of the foodstuff. This relative movement occurs preferablythroughout the entire volume of the foodstuff during the treatmentprocess. It is believed that the relative movement caused bymanipulating apparatus 10 damages the cell walls of microbes in thefoodstuff, thereby killing the microbes. This damage to the microbes maybe accomplished as ice crystals are pressed against the microbe cellwalls in the course of the manipulation. The microbes may also becomebrittle at the processing temperature employed by the invention and themanipulation may serve to damage the cell walls in this relativelybrittle state. Although the mechanism by which microbe kill isaccomplished is not fully understood, tests of the apparatus and processaccording to the invention indicate significant microbe kill.

The freezer 12 may be any suitable device capable of cooling thefoodstuff to a process temperature no greater than or below the freezingpoint of the foodstuff. For example, freezer 12 may comprise aroller-type freezer as disclosed in U.S. Pat. Nos. 4,138,768 and4,192,899, which are incorporated herein by this reference. Regardlessof the particular type of freezer employed, freezer 12 preferablyfreezes the foodstuff in less than thirty (30) minutes and optimally inless than about ten (10) minutes. The roller-type freezer disclosed inU.S. Pat. Nos. 4,138,768 and 4,192,899 is particularly well-suited forrapidly freezing foodstuffs into thin sheets of material which may thenbe cut into small sections. Freezing times of approximately 2 minutesmay be obtained using these roller-type freezers. Regardless of thefreezer type, rapid freezing is preferable for purposes of thisinvention because rapid freezing produces relatively smaller icecrystals as compared to a slow freezing process. It is believed that thesmaller ice crystals produced by rapidly freezing a foodstuff improvemicrobe kill during the manipulation or stressing step according to theinvention.

Freezer 12 also preferably has associated with it a forming arrangementfor forming the pH modified foodstuff into workpieces comprisingdiscrete pieces of foodstuff. The forming arrangement may comprise thecutting system 18 such as the cutting system shown in U.S. Pat. No.4,192,899. This cutting arrangement 18 cuts workpieces from the sheet offrozen foodstuff produced by freezer 12. Alternatively, the foodstuffmay be formed into workpieces in an unfrozen state and then frozen tothe process temperature. In any event, the workpieces preferablycomprise approximately half-inch by half-inch squares having a thicknessof approximately 0.25 to 0.125 inches. Although larger workpieces may beused within the scope of invention, the thickness of workpieces ispreferably less than 0.75 inches. The thinness of the workpiece helpsensure relative movement throughout the volume of the workpiece as theworkpiece is manipulated according to the invention. Also, thin sheetsor workpieces of foodstuff may be cooled more quickly to the processtemperature.

Transport device 14 preferably comprises a vibrating conveyor capable ofreceiving the frozen workpieces from freezer 12 and cutter system 18,and transporting the workpieces to an inlet 20 associated withmanipulating apparatus 10. Details of the transport device 14 are notshown in the figures since a number of different types of conveyingdevices may be employed within the scope of invention, and in any eventthe details of such conveying devices are well within the knowledge ofthose skilled in the present field. Transport device 14 preferably movesthe frozen workpieces quickly to the manipulating, device 10 so that theworkpieces are manipulated as quickly as possible after being frozen tothe process temperature. It is believed that microbes which have beenmaintained at the process temperature for a long period of time cansurvive the manipulation better. In the preferred form of the invention,manipulating device 10, freezer 12, and transport device 14 are situatedand operated such that the workpieces are manipulated according to theinvention as quickly as possible after reaching the process temperature,and preferably no more than about ten (10) minutes, about thirty (30)minutes, or about one hour, or as much as 24 hours, after the workpiecesreach the process temperature, although longer periods may be usedwithin the scope of the invention.

One preferred manipulating apparatus 10 is shown in FIGS. 2 and 3.Manipulating apparatus 10 includes a chute 22 through which workpieces23 drop from the transport device 14 shown in FIG. 1. The illustratedmanipulating apparatus 10 includes two spaced apart rollers 24 and 25within a chamber 26. Rollers 24 and 25 are positioned within chamber 26with their longitudinal axes extending substantially parallel to eachother. Chamber walls 28 are positioned on either side of the tworollers. Rollers 24 and 25 are spaced apart with a minimum clearancebetween the roller surfaces which is less than an initial thickness ofthe workpieces 23. For example, workpieces 23 may be approximately 0.25to 0.125 inches thick and the clearance between the opposing surfaces ofrollers 24 and 25 may be approximately 0.10 inches. The spaced apartrollers 24 and 25 define a working area W extending from the point ofminimum clearance between the roller surfaces upwardly to a point atwhich workpieces 23 first make contact with both rollers.

At least one of the rollers 24 or 25 is driven by a suitable drive motorso as to rotate about its longitudinal axis. The direction of rotationis toward the opposing roller. In the illustrated form of the invention,both rollers 24 and 25 are driven by a single drive motor 30 in acounter rotating fashion toward each other. Drive motor 30 drives firstroller 24 directly through shaft 32 and timing gears 34 and 35 cooperateto drive the second roller 25. Timing gear 34 is mounted on drive shaft32 while timing gear 35 is mounted on drive shaft 33 which is rigidlyconnected to second roller 25. Although not shown in the drawings, thoseskilled in the art will appreciate that drive motor 30 includes asuitable transmission arrangement for transmitting power to the firstdrive shaft 32. The drive motor 30 and associated transmissionarrangement may be adapted for driving rollers 24 and 25 at a constantspeed, or may be adapted to vary the speed to suit different processingrates.

Although rollers 24 and 25 may have a substantially smooth outersurface, the illustrated preferred rollers include longitudinallyextending ridges 38. Rollers 24 and 25 are rotated in synchronizationthrough the timing gears 34 and 35 so that each ridge 38 on one rollerregisters between adjacent ridges on the opposing roller similarly tothe cogs of two intermeshed gears. flowever, the ridges 38 on theopposing rollers preferably do not touch, but always maintain a minimumclearance between the opposing roller surfaces, for exampleapproximately 0.10 inches.

The manipulating apparatus 10 shown in FIGS. 2 and 3 also preferablyincludes a manipulator temperature control system for cooling or warmingthe outer surfaces of rollers 24 and 25, that is, the surfaces of themanipulating apparatus which may come in contact with workpieces 23.Maintaining the outer surface of rollers 24 and 25 at a temperature nearthe process temperature prevents the rollers from heating workpieces 23above the process temperature as the workpieces come in contact with theroller surfaces. A roller outer surface temperature which is near butjust above the particular process temperature being employed also helpsprevent workpieces 23 from sticking to the rollers 24 and 25 and mayalso enhance microbe kill as discussed below. For example, the outersurfaces of the rollers 24 and 25 may be maintained at approximately 32degrees Fahrenheit where the process temperature is approximately 28degrees Fahrenheit or lower.

The illustrated temperature control system includes for each roller 24and 25 an inlet 40 and an outlet 41. A channel 42 extends near the outersurface of the respective roller and is preferably formed as acontinuous spiral groove between an inner roller member 44 and an outerroller member 45. A temperature controlling fluid is circulated throughan inlet duct 48 associated with respective roller drive shaft 32 and 33into the inlet 40, through the continuous spiral channel 42, and outthrough outlet port 41 and outlet duct 49 formed in respective driveshaft. Any suitable fluid may be circulated through the temperaturecontrol system for cooling or heating the outer surfaces of rollers 24and 25 preferably to a temperature near the processing temperature, thatis, the temperature of the frozen workpieces as they pass between therollers. The system for producing the temperature control fluid,directing the fluid into inlet duct 48, and receiving the returningfluid from outlet duct 49 is omitted from the drawings so as not toobscure the invention in unnecessary detail. Such system is within theknowledge of those skilled in the art.

The roller-type manipulating apparatus 10 shown in FIGS. 2 and 3 alsopreferably includes gas injection ports 52. Any suitable gas such asclean air may be injected through the gas injection ports 52 so as toflow over the outer surfaces of rollers 24 and 25. The injected gashelps clean the roller surfaces and separate foodstuff material whichmay partially stick to the roller surfaces.

In operation, the roller-type manipulating apparatus 10 shown in FIGS. 2and 3 receives a plurality of workpieces 23 into chamber 26 immediatelyabove rollers 24 and 25. As at least one of the rollers is rotatedtoward the opposite roller or both rollers are rotated toward each otherin counter rotating fashion, workpieces 23 are drawn into the workingarea W and through the area of minimum clearance between the rollers.This action in shown best in FIGS. 4 through 6. Referring to FIGS. 4 and5 each frozen workpiece retains generally its initial shape beforepassing into the working area W between rollers 24 and 25. However, asshown in FIG. 6, the workpiece material is forced to spread outlaterally as the workpiece passes through the working area W andultimately through the area of minimum clearance between rollers 24 and25. This spreading of the workpiece material causes rclativc movementbetween points within the volume of the material. For example, referringto FIG. 5, a central point A in workpiece 23 resides a distance d to apoint B at one corner of the workpiece. However, as the workpiece 23spreads out as it passes between rollers 24 and 25 as shown in FIG. 6,the distance d between point A and point B changes significantly. Thisrelative movement would occur even if rollers 24 and 25 each had asmooth outer surface. The ridged rollers 24 and 25 have the addedadvantage of forcing the workpiece material to bend around the opposingridges 38. This bending in the workpiece material produces additionalrelative movement between various points within the material.

In the preferred form of the invention, the manipulating arrangementcauses relative movement throughout the volume of the foodstuff beingprocessed. Relative movement throughout the foodstuff ensures consistentmicrobe kill throughout the foodstuff. However, manipulation whichproduces relative movement in only a portion of the material beingprocessed produces microbe kill in that portion of the material in whichthe relative movement occurs. Significant microbe kill can beaccomplished according to the invention by manipulating the frozencomminuted foodstuff so as to produce relative movement in at leastapproximately twenty percent of the volume of the foodstuff. In theroller-type manipulating arrangement disclosed in FIGS. 1 through 6, theextent of relative movement in the workpieces is controlled primarily bythe clearance between the rollers relative to the initial thickness ofthe workpieces. A clearance between rollers equal to ninety-five percent(95%) or less of the total initial thickness of the individualworkpieces produces the desired relative movement in a significantvolume of the foodstuffs being processed.

FIG. 7 shows an alternate manipulating arrangement 60 according to theinvention. In the form of invention shown in FIG. 7, workpieces (notshown in FIG. 7) are collected in an area 62 bounded by at least onemovable plate. The form of invention shown FIG. 7 has both a movable topplate or platen 64 and a movable bottom plate or platen 65. Both topplate 64 and bottom plate 65 are movable along axis M relative tochamber walls 68. A top actuator 70 is associated with top plate 64while a bottom actuator 71 is associated with bottom plate 65. Actuator70 may comprise a suitable hydraulic or pneumatic piston and cylinderunit for positioning the top plate 64 along the axis M. Actuator 71 maysimilarly comprise a piston and cylinder arrangement for positioningbottom plate 65 along axis M. Chamber walls 68 may each have a structure72 which allows a temperature control fluid to be circulated therethrough for cooling or heating the chamber walls to a temperature nearthe process temperature similarly to the rollers 24 and 25 discussedabove with particular reference to FIGS. 2 and 3.

In operation, numerous small workpieces (not shown in FIG. 7) arerandomly arranged in the area 62 defined by bottom plate 65 and chamberwalls 68. The random arrangement of rigid small workpieces in the area62 leaves numerous voids between the individual workpieces. Once thearea is filled to a desired point, top actuator 70 is operated to movethe top plate downwardly toward bottom plate 65 and into the area 62defined between the chamber walls 68. A lowered position of top plate 64is shown in phantom in FIG. 7. As top plate 64 advances toward bottomplate 65, the workpieces deform to fill the voids in the volume. Thisdeformation produces relative movement throughout each workpiece.

Top plate 64 may be advanced downwardly until the individual workpieces(not shown in FIG. 7) in area 62 deform to produce substantially a solidblock of material. At is point, bottom actuator 71 may be operated tomove bottom plate 65 downwardly along axis M as top plate 64 continuesdownwardly. This downward movement of both top plate 64 and bottom plate65 pushes the block formed from the frozen workpieces out from betweenchamber walls 68. Once the block clears chamber walls 68, the block offrozen material may be transferred by suitable means to another locationfor packaging for further processing.

Manipulating apparatus 60 shown in FIG. 7 is used in connection with afreezer and a transport device which are not shown in the drawing. Thefreezer may be the same type of freezer discussed with reference to FIG.1. The transport device may be any suitable conveyor or other device fortransporting the frozen, pH modified workpieces from the freezer to thechamber area 62. The freezer preferably freezes the workpieces in lessthan 30 minutes and optimally in less than 10 minutes. Relatively smallworkpieces are preferable for use in the manipulating arrangement shownin FIG. 7. Workpieces having a size on the order of 0.5 inches by 0.5inches by 0.25 inches ensure consistent relative movement within eachworkpiece. However larger or smaller thin pieces of frozen comminuted orground foodstuffs may be effectively treated with the apparatus 60 shownin FIG. 7.

The manipulating process according to the invention is particularlyapplicable to comminuted foodstuffs. As used in this disclosure and inthe following claims, a comminuted foodstuff may comprise any ground,chopped, or mixed foodstuff which is made up of relatively small piecesof foodstuffs which have been cut down or otherwise formed from largerpieces. The invention is well suited for treating ground meat such asbeef, pork, or poultry. In the following examples, the process wasapplied to comminuted beef products. However, the invention may be usedto treat substantially any comminuted foodstuff.

The manipulation according to the invention provides an immediatereduction in microbe count. However, microbe count decreases further fora period of time after the manipulation is performed. It is thereforepreferable to use the processed foodstuffs no sooner than approximately24 hours after the manipulation is performed. In this sense “use” thefoodstuffs means cook the product or incorporate it into another foodproduct.

Regardless of the particular manipulation arrangement used, it may bedesirable to cause at least a portion of each workpiece to go to anunfrozen state during the physical manipulation step. As used in thisdisclosure and the following claims, an “unfrozen” state means a statein which some, but not necessarily all, ice crystals formed in thefoodstuff when the foodstuff was cooled to the process temperature goback to a liquid state. Placing a portion of each workpiece an unfrozenstate may be accomplished by the pressure applied in the manipulationstep or may be accomplished by increasing the temperature of a portionof each workpiece during the manipulation step to the freezing point ofthe foodstuff or slightly above the freezing point. After physicallymanipulating or stressing the workpieces, each workpiece is re-frozen tothe process temperature, that is, a temperature no greater than or belowthe freezing point of the foodstuff. The workpieces may be re-frozen bycooling them in a suitable freezing device or by allowing the stillfrozen portions of the workpieces to re-freeze the adjacent unfrozenportions. Also, re-freezing may be accomplished in some cases simply byremoving the pressure applied during the manipulation step.

EXAMPLE 1

A test was performed using a block-type manipulation apparatus similarto that illustrated in FIG. 7. Two batches of foodstuffs were processedin the apparatus. A first batch comprised regular ground beef having apH of approximately 5.25 to 5.5. A second batch was made up of groundbeef mixed with 15% (by weight) lean finely textured beef having a pH ofapproximately 6.25 to 6.5. The ground beef used in the second batch wastaken from the same lot as the ground beef used in the first batch. Itwill be noted that the pH increase in the second batch was accomplishedby mixing the higher pH lean finely texture beef with the lower pHground beef.

The first batch comprising regular ground beef was first processedthrough a grinder having 0.125 inch diameter grinder plate openings.Five samples of the ground beef material were taken at the grinderoutput, the samples taken approximately 10 seconds apart. The groundbeef was then cooled to approximately 28 degrees Fahrenheit (atemperature below the freezing point of the ground beef material) inabout two minutes using a roller-type freezing machine described above.The frozen ground beef was cut into workpieces with a cutting machineassociated with the roller-type freezer, the workpieces being aboutone-eighth inch thick and measuring approximately one-half inch byone-half inch. Five samples were taken at the output of thefreezer/cutter arrangement.

The workpieces of ground beef at the process temperature were thenplaced in a block-type manipulating device similar to that shown in FIG.7. The working area of the device was filled loosely with the workpiecesand then the volume of the loose collection of workpieces was reduced byabout 50% to form a block of frozen ground beef. The volume reductionwas achieved by advancing a top plate. The block of material was thenremoved from the manipulating device and samples of material were coredat various locations around the block. These cores were mixed togetherand five samples of frozen material were then collected from the mix ofcored material.

Tables 1 through 3 show the results of bacteria tests performed on thevarious samples described above. Tests were conducted for total Platecount (TIC), E.Coli Count, Coliform count, and Staph count. Tests werealso conducted to detect the presence of Salmonella and Listeria. Table1 shows the results for the five samples taken at the grinder output.Table 2 shows the results for the five samples taken at thefreezer/cutter output. Table 3 shows the bacteria test results for thefive samples taken from the material removed from the frozen block.Comparing Table 3 to Tables 1 and 2, the freezing and manipulation aloneproduced a reduction in Coliform and Staph counts in the ground beef.

TABLE 1 Sample TPC E. Coli Coliform Staph Sal. List 1 7,800 20 150 43Neg Neg 2 6,000 40 130 23 Neg Pos 3 13,000 10 720 7 Neg Neg 4 4,600 30490 9 Pos Neg 5 4,700 90 910 43 Neg Pos Avg 7,220 38 480 25 N/A N/A

TABLE 2 Sample TPC E. Coli Coliform Staph Sal. List 1 20,000 10 250 23Pos Neg 2 9,200 40 490 4 Neg Pos 3 16,000 10 720 9 Neg Neg 4 5,100 10130 7 Neg Neg 5 6,900 20 680 23 Neg Neg Avg 11,440 18 454 13.2 N/A N/A

Table 3 Sample TPC E. Coli Coliform Staph Sal. List 1 7,600 10 110 9 NegNeg 2 5,900 20 200 3 Neg Neg 3 6,100 10 270 3 Neg Pos 4 750 10 210 9 NegNeg 5 6,700 20 400 3 Neg Neg Avg 5,410 14 238 5.4 N/A N/A

The second batch of beef material, comprising the ground beef mixed with15% lean finely textured beef, was processed in the same fashion as thefirst batch and samples were taken in the same fashion and at the samepoints. Tables 4 through 6 show the results of bacteria tests performedon the samples from the second batch. Table 4 shows the results for thefive samples taken at the grinder output. Table 5 shows the results forthe five samples taken at the freezer/cutter output. Table 6 shows thebacteria test results for the five samples taken from the materialremoved from the frozen block. Comparing the Table 6 test results withthose of Tables 4 and 5, there was a marked reduction in Total Platecount, E. Coli count, Coliform count, and Staph count in the samplestaken after pH manipulation and manipulation in the block-typemanipulation device. The “<” symbol in Table 6 indicates that theobserved count was less than the minimum resolution for the test. Also,all tests for Salmonella and Listeria were negative in the materialsubjected to both pH manipulation and physical manipulation according tothe invention.

TABLE 4 Sample TPC E. Coli Coliform Staph Sal. List 1 29,000 90 720 7Neg Neg 2 8,600 40 490 4 Pos Neg 3 13,000 180 270 43 Pos Neg 4 4,600 2201,600 23 Neg Pos 5 6,000 110 200 23 Neg Pos Avg 12,240 128 656 20 N/AN/A

TABLE 5 Sample TPC E. Coli Coliform Staph Sal. List 1 5,800 10 110 9 NegNeg 2 3,400 40 200 4 Neg Pos 3 3,900 10 270 7 Neg Neg 4 3,100 10 210 4Neg Neg 5 5,300 20 400 9.1 Neg Neg Avg 4,300 18 238 6.6 N/A N/A

TABLE 6 Sample TPC E. Coli Coliform Staph Sal. List 1 2,900 <10 10 <3Neg Neg 2 2,700 <10 <10 <3 Neg Neg 3 2,000 <10 10 <3 Neg Neg 4 300 <10<10 <3 Neg Neg 5 900 <10 10 <3 Neg Neg Avg 1,760 <10 <3 N/A N/A

The above described preferred embodiments are intended to illustrate theprinciples of the invention, but not to limit the scope of theinvention. Various other embodiments and modifications to thesepreferred embodiments may be made by those skilled in the art withoutdeparting from the scope of the following claims. For example, a screwpress or compressor may be used as the manipulating device in place ofthe block forming arrangement shown in FIG. 7 or roller-typemanipulating device shown in FIGS. 2 and 3. Also, although the inventionis described as processing individual workpieces formed from thefoodstuff to be treated, the roller-type treatment apparatus such asthat shown in FIGS. 2 and 3 may operate on a substantially continuousstrand or strands of frozen foodstuff. Each such strand is to beconsidered an equivalent of the workpieces described above and set outin the following claims.

What is claimed is:
 1. An apparatus for reducing microbe content in comminuted foodstuffs, the apparatus comprising: (a) a pH modifying arrangement for modifying the pH of a comminuted foodstuff to be processed to produce a pH modified comminuted foodstuff; (b) a freezer for cooling a workpiece of the pH modified comminuted foodstuff to a temperature below the freezing point of the pH modified comminuted foodstuff; and (c) a manipulating arrangement for manipulating the workpiece to produce relative movement between points throughout a portion of the workpiece while the workpiece is at a temperature below the freezing point of the pH modified comminuted foodstuff.
 2. The apparatus of claim 1 further comprising: (a) a manipulator temperature system for controlling the temperature of the surfaces of the manipulating arrangement which come in contact with the workpiece.
 3. The apparatus of claim 1 wherein the manipulating arrangement comprises: (a) a first roller, (b) a second roller having a rotational axis substantially parallel to a rotational axis of the first roller, the second roller being spaced apart from the first roller such that the clearance between the first roller and second roller is less than the initial thickness of the workpiece so that the workpiece is compressed and allowed to expand laterally as the workpiece is drawn between the first roller and second roller; and (c) a drive arrangement for driving at least the first roller about its rotational axis toward the second roller.
 4. The apparatus of claim 3 wherein: (a) the drive arrangement drives both the first roller and the second roller in a counter rotating fashion; and (b) the surface of the first roller and the second roller each include circumferentially spaced apart longitudinal ridges, each ridge on the first roller registering with a space between adjacent ridges on the second roller as the rollers rotate about their respective longitudinal axis.
 5. The apparatus of claim 3 wherein the workpiece has an initial thickness of between 0.25 inches and 0.125 inches and the clearance between the first roller and second roller is approximately 0.10 inches.
 6. The apparatus of claim 1 wherein the temperature at which the workpiece is manipulated is no greater than 28 degrees Fahrenheit.
 7. The apparatus of claim 1 wherein the freezer brings the temperature of the foodstuff from an initial temperature above freezing to the temperature below the freezing point of the pH modified comminuted foodstuff in no more than thirty minutes.
 8. The apparatus of claim 1 wherein the pH modifying arrangement includes a supply of pH increasing material and an application device within which the comminuted foodstuff to be processed is exposed to the pH increasing material for a period of time sufficient to raise the pH of the comminuted foodstuff.
 9. The apparatus of claim 8 wherein the pH increasing material comprises NH₃ gas.
 10. An apparatus for manipulating discrete pieces of comminuted foodstuffs to decrease the microbe content thereof, the apparatus comprising: (a) a pH modifying arrangement for modifying the pH of a comminuted foodstuff to be processed to produce a pH modified comminuted foodstuff; (b) a freezing and forming device for receiving the pH modified comminuted foodstuff and producing a plurality of workpieces, each workpiece comprising a discrete piece made up of a quantity of the pH modified comminuted foodstuff at a temperature below the freezing point of the pH modified comminuted foodstuff; and (c) a manipulating arrangement for receiving the plurality of workpieces and for manipulating the workpieces to produce relative movement between points throughout a portion of each workpiece while each respective workpiece is at a temperature below the freezing point of the pH modified comminuted foodstuff.
 11. The apparatus of claim 10 wherein each workpiece has an initial thickness of between 0.25 inches and 0.125 inches.
 12. The apparatus of claim 10 wherein the temperature below the freezing point of the pH modified comminuted foodstuff is no greater than approximately 28 degrees Fahrenheit.
 13. The apparatus of claim 10 wherein the freezing and forming device operates to bring the foodstuff from an initial temperature over the freezing point of water to no greater than 28 degrees Fahrenheit in no more than thirty minutes.
 14. The apparatus of claim 10 wherein the manipulating arrangement comprises: (a) a press having a first plate in a spaced apart relationship with a second plate and also having an actuator system for decreasing the distance between the first plate and second plate to manipulate the workpieces.
 15. The apparatus of claim 10 wherein the pH modifying arrangement includes a supply of NH₃ gas and a device through which the comminuted foodstuff to be processed may be exposed to the NH₃ gas for a period of time sufficient to raise the pH of the comminuted foodstuff.
 16. An apparatus for reducing microbe content in comminuted meat products, the apparatus comprising: (a) a pH modifying arrangement for modifying the pH of a comminuted meat product to produce a pH modified comminuted meat product; (b) a freezer for cooling a workpiece of the pH modified comminuted meat product to a temperature below the freezing point of the pH modified comminuted meat product, the workpiece comprising a piece of material made up of a quantity of the pH modified comminuted meat product; and (c) a manipulating arrangement for manipulating the workpiece to produce relative movement between points throughout the workpiece while the workpiece is at a temperature below the freezing point of the pH modified comminuted meat product.
 17. The apparatus of claim 16 wherein the pH modifying arrangement includes a device for applying NH₃ gas to the comminuted meat product to produce the pH modified comminuted meat product.
 18. The apparatus of claim 16 wherein the manipulating arrangement comprises: (a) a first roller, (b) a second roller having a rotational axis substantially parallel to a rotational axis of the first roller, the second roller being spaced apart from the first roller such that the clearance between the first roller and second roller is less than the initial thickness of the workpiece so that the workpiece is compressed and allowed to expand laterally is the workpiece is drawn between the first roller and second roller; and (c) a drive arrangement for driving one of the first roller or second roller about its respective rotational axis toward the other one of the first roller or second roller.
 19. The apparatus of claim 16 wherein the manipulating arrangement comprises a press having a first plate in a spaced apart relationship with a second plate to define a working area in which to receive the workpiece together with a plurality of additional workpieces, and also having an actuator system for decreasing the distance between the first plate and second plate. 